Volunteering a Public Service: An Experimental Investigation

In some public goods environments it may be advantageous for heterogeneous groups to be coordinated by a single individual. This “volunteer” will bear private costs for acting as the leader while enabling each member of the group to achieve maximum potential gains. This environment is modeled as a War of Attrition game in which everyone can wait for someone else to volunteer. Since these games generally have multiple Nash equilibria but a unique subgameperfect equilibrium, we tested experimentally the predictive power of the subgame-perfection criterion. Our data contradict that subjects saw the subgame-perfect strategy combination as the obvious way to play the game. An alternative behavioral hypothesis – that subjects were unable to predict accurately how their opponents would play and tried to maximize their expected payoff – is proposed. This hypothesis fits the observed data generally well.

Relaxing the I.I.D. Assumption: Adaptively Minimax Optimal Regret via Root-Entropic Regularization

We consider sequential prediction with expert advice when data are generated from distributions varying arbitrarily within an unknown constraint set. We quantify relaxations of the classical i.i.d. assumption in terms of these constraint sets, with i.i.d. sequences at one extreme and adversarial mechanisms at the other. The Hedge algorithm, long known to be minimax optimal in the adversarial regime, was recently shown to be minimax optimal for i.i.d. data. We show that Hedge with deterministic learning rates is suboptimal between these extremes, and present a new algorithm that adaptively achieves the minimax optimal rate of regret with respect to our relaxations of the i.i.d. assumption, and does so without knowledge of the underlying constraint set. We analyze our algorithm using the follow-the-regularized-leader framework, and prove it corresponds to Hedge with an adaptive learning rate that implicitly scales as the square root of the entropy of the current predictive distribution, rather than the entropy of the initial predictive distribution.Comment: 71 pages, 2 figures. Blair Bilodeau and Jeffrey Negrea are equal-contribution authors; order was determined randoml

Minimax optimal quantile and semi-adversarial regret via root-logarithmic regularizers

Quantile (and, more generally, KL) regret bounds, such as those achieved by NormalHedge (Chaudhuri, Freund, and Hsu 2009) and its variants, relax the goal of competing against the best individual expert to only competing against a majority of experts on adversarial data. More recently, the semi-adversarial paradigm (Bilodeau, Negrea, and Roy 2020) provides an alternative relaxation of adversarial online learning by considering data that may be neither fully adversarial nor stochastic (i.i.d.). We achieve the minimax optimal regret in both paradigms using FTRL with separate, novel, root-logarithmic regularizers, both of which can be interpreted as yielding variants of NormalHedge. We extend existing KL regret upper bounds, which hold uniformly over target distributions, to possibly uncountable expert classes with arbitrary priors; provide the first full-information lower bounds for quantile regret on finite expert classes (which are tight); and provide an adaptively minimax optimal algorithm for the semi-adversarial paradigm that adapts to the true, unknown constraint faster, leading to uniformly improved regret bounds over existing methods.https://arxiv.org/pdf/2110.14804.pdfPublished versio

Changes in specific metabolic pathways are essential steps in the early apoptotic process in the liver

the immunosuppressant Cyclosporine A (CsA), we used multinuclear NMR spectroscopy and molecular studies to characterize metabolic pathways in mice liver during anti-Fas-induced apoptosis. An upregulation of specific metabolic pathways of glucose was the earliest indicator of the effect of Fas on the liver. CsA prevented apoptosis and energy failure at late stages, while the reversal of Fas-induced metabolic upregulation at early stages preceded the protective effect of EGF on programmed cell death. These phenomena provide useful hints for the understanding of early mechanisms controlling apoptotic cell death

RNA splicing at human immunodeficiency virus type 1 3 ' splice site A2 is regulated by binding of hnRNP A/B proteins to an exonic splicing silencer element

The synthesis of human immunodeficiency virus type 1 (HIV-1) mRNAs is a complex process by which more than 30 different mRNA species are produced by alternative splicing of a single primary RNA transcript. HIV-1 splice sites are used with significantly different efficiencies, resulting in different levels of mRNA species in infected cells. Splicing of Tat mRNA, which is present at relatively low levels in infected cells, is repressed by the presence of exonic splicing silencers (ESS) within the two tat coding exons (ESS2 and ESS3). These ESS elements contain the consensus sequence PyUAG. Here we show that the efficiency of splicing at 3 ' splice site A2, which is used to generate Vpr mRNA, is also regulated by the presence of an ESS (ESSV), which has sequence homology to ESS2 and ESS3. Mutagenesis of the three PyUAG motifs within ESSV increases splicing at splice site A2, resulting in increased Vpr mRNA levels and reduced skipping of the noncoding exon flanked by A2 and D3. The increase in Vpr mRNA levels and the reduced skipping also occur when splice site D3 is mutated toward the consensus sequence. By in vitro splicing assays, we show that ESSV represses splicing when placed downstream of a heterologous splice site. A1, A1(B), A2, and B1 hnRNPs preferentially bind to ESSV RNA compared to ESSV mutant RNA. Each of these proteins, when added back to HeLa cell nuclear extracts depleted of ESSV-binding factors, is able to restore splicing repression. The results suggest that coordinate repression of HIV-1 RNA splicing is mediated by members of the hnRNP A/B protein family

Origin and implications of the observed rhombohedral phase in nominally tetragonal Pb(Zr\u3csub\u3e0.35\u3c/sub\u3eTi\u3csub\u3e0.65\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e thin films

The structural and electrical properties of Pb(Zr0.35Ti0.65)O3 (PZT) thin films ranging in thickness from 700 to 4000 Å have been investigated. These (001)/(100)-textured films were grown by metalorganic chemical vapor deposition on (111)-textured Ir bottom electrodes. It was observed that, in the as-deposited state, the thinnest PZT films are rhombohedral even though bulk PZT of this composition should be tetragonal. Thicker films have a layered structure with tetragonal PZT at the surface and rhombohedral PZT at the bottom electrode interface. In this article we investigate the origin of this structure and its effect of the ferroelectric and dielectric properties of PZT capacitors. It has been suggested that thin films stresses can affect the phase stability regions of single domain PZT. This possibility has been investigated by piezoresponse microscopy and thin film stress measurements. In the as-deposited state the majority of PZT grains contain a single ferroelastic domain, whereas after a high temperature anneal, a large fraction of the grains contain several ferroelastic domains. Wafer curvature measurements in combination with x-ray diffraction stress measurements in the Ir bottom electrode showed that the as-deposited PZT films are, within experimental error, stress free at room temperature. Landau–Ginbzurg–Devonshire formalism was used to explain the origin of the rhombohedral phase as a result of substrate constraint on single domain PZT grains. Annealing was found to affect the relative volume fractions of the rhombohedral and tetragonal phases and the electrical properties of PZT films. Intermediate temperature anneals increased the volume fraction of the rhombohedral phase and the coercive field extracted from the polarization-electric field hysteresis loops. After a high temperature anneal (650 °C) the majority of the grains transformed into a polydomain state, decreasing the volume fraction of the rhombohedral phase and the coercive field. If the high temperature anneal was performed after deposition of the top electrode, the coercive field became independent of the PZT thickness

Early quantitative coronary angiography of saphenous vein grafts for coronary artery bypass grafting harvested by means of open versus endoscopic saphenectomy: a prospective randomized trial

AbstractObjectiveEndoscopic saphenectomy is associated with a decreased incidence of wound complications without an increase in histologic trauma or endothelial dysfunction in published reports. Concern remains about the patency of saphenous vein grafts harvested endoscopically and the development of early intimal hyperplasia. The purpose of this study was to compare early quantitative coronary analysis of saphenous vein grafts used for coronary artery bypass grafting harvested with the open versus endoscopic techniques.MethodsForty patients undergoing primary coronary artery bypass grafting surgery with at least 1 saphenous vein graft were randomized preoperatively to open versus endoscopic saphenectomy with bipolar cauterization of side branches. Quantitative coronary angiography was performed a mean of 3 months (range, 1-9 months) after the operation.ResultsThere was no statistically significant difference in the patency rates of internal thoracic artery grafts between the open and endoscopic groups and no statistically significant difference in the patency rates of saphenous vein grafts between both groups (85.2% vs 84.4%, P = .991). Quantitative coronary angiography showed no difference in graft stenosis (≥50% of the internal diameter of the graft) in the body of the saphenous vein grafts in the open versus endoscopic saphenectomy groups (3.7% vs 0%, P = .280).ConclusionAngiographic appearance and patency rates of saphenous vein grafts harvested with the endoscopic technique are similar to those of saphenous vein grafts harvested with the open technique. These results support the use of endoscopic saphenectomy because of the known lower incidence of wound and infectious complications and superior functional results

Automated CO2 and CH4 monitoring system for continuous estimation of degassing related to hydropower

Reliable measurement of greenhouse gas emissions from reservoirs is essential for estimating the carbon footprint of the hydropower industry. Among the different emission pathways, degassing downstream of the turbines and spillway is poorly documented mainly because of the safety stakes related to sampling up and downstream the power plants. The alternative being to sample the water from the turbine inside the station, this study aimed to assemble a custom automated CO2 and CH4 monitoring system (SAGES), especially designed for long-term surveys in hydropower facilities, with a special focus on low maintenance requirements. The SAGES combines infrared and laser technologies with a modular programming approach and run with a specifically designed plexiglass equilibration system (PES) that maintain a permanent headspace and avoid clogging by suspended solids. Although the SAGES is based on commercially available devices, it is the first time they are combined and used with the gas equilibrator. To ensure the reliability of the mounting and to control the quality of the readings, the system was tested in laboratory prior to its installation in generating stations. SAGES and PES performances were compared with those of generic devices available on the market although less adapted to the specific deployments targeted. The SAGES gas partial pressure measurements were accurate and linear in the entire range tested: 0 to 5,000 ppm for pCO2 and 0 to 600 and 10,000 ppm for pCH4. Gas PP measurements were comparable to the reference CO2/CH4 sensor and there was no drift during long term deployment. The SAGES/PES installed in 2021 in cascading generating stations of the Romaine complex collected more than 28,000 data points over a 10-month period and required only two maintenances. Results show that the SAGES is a reliable tool that provide long-term CO2 and CH4 dataset in generating stations while requiring minimal energy, care and maintenance. The data collected in turbine water and the recent use of the SAGES in peat land by a collaborative team demonstrate how the SAGES systems can efficiently contribute to the understanding of reservoir carbon cycles